A large majority of priests in the Vatican are gay, although many are not sexually active, a new book claims.

A total of about 80 percent of the most revered clerics in the Roman Catholic Church are homosexual despite the church’s opposition to gay rights, according to the extensively researched book by French journalist Frédéric Martel.

The gay priests adhere to an unspoken code called “the closet,” where it is understood that, for instance, a cardinal or bishop who denounces homosexuality is more likely to be gay, according to the book “In the Closet of the Vatican.”

Another controversial claim in the book is that Colombian Cardinal Alfonso López Trujillo defended the church’s positions on homosexuality while hiring male prostitutes, according to The Guardian.

The author said he conducted 1,500 interviews with 41 cardinals, 52 bishops and monsignors, 45 papal ambassadors or diplomatic officials, 11 Swiss guards and more than 200 priests and seminarians.

The book attempts to expose a “clerical culture of secrecy” and the double lives of priests.